(2cos20°-sin10°)/sin80°
问题描述:
(2cos20°-sin10°)/sin80°
化简求值
答
(2cos20°-sin10°)/sin80°=(2cos20°-cos80°)/sin80°=[cos20°+(cos20°-cos80°)]/sin80°={cos20°+[cos(50°-30°)-cos(50°+30°)]}/[sin80°]={cos20°+[2sin30°sin50°]}/sin80°={cos20°+sin50°}/sin8...